Senators on both sides of the aisle responded quickly to the U.S. Army Corps of Engineers’ decision to halt construction of the Dakota Access pipeline beneath a Missouri River reservoir.

This newest development in the months-long Standing Rock saga has left protesters optimistic about pushing for an alternative pipeline route, but they remain wary of a policy reversal once Donald Trump takes office in January, according to The Associated Press.

The Corps on Sunday refused to approve an easement that would have allowed part of the pipeline to be built under Lake Oahe, potentially threatening the Standing Rock Sioux tribe’s drinking water and cultural sites.

Following the decision, Democratic North Dakota junior Sen. Heidi Heitkamp criticized the Obama administration for delaying action on pipeline construction and voiced concerns over the safety of protesters during North Dakota's bitter winter.

“This administration’s delay in taking action — after I’ve pushed the White House, Army Corps, and other federal agencies for months to make a decision — means that today’s move doesn’t actually bring finality to the project,” Hetikamp said in a statement. “The pipeline still remains in limbo.”

Heitkamp met with President-elect Donald Trump on Friday in New York City to discuss the ongoing protests, inducing speculation she is being considered for a cabinet-level position.

Heitkamp's Republican counterpart, Sen. John Hoeven, responded in kind, arguing the Corps’ decision “violates the rule of law and fails to resolve the issue.”

“Instead, it passes the decision off to the next administration,” Hoeven added, “which has already indicated it will approve the easement, and in the meantime perpetuates a difficult situation for North Dakotans.”

Former Democratic presidential candidate Sen. Bernie Sanders praised the decision and thanked Obama for listening to the protesters.

“I appreciate very much President Obama listening to the Native American people and millions of others who believe this pipeline should not be built,” Sanders said in a statement.

I appreciate @POTUS listening to the Native Americans and millions of others who believe the Dakota Access Pipeline shouldn't be built.

Energy Transfer Partners, one of the companies involved in construction of the pipeline, did not share Sanders’ enthusiasm. The company condemned the decision as a "purely political action," and called the delay "the latest in a series of overt and transparent political actions by an administration which has abandoned the rule of law in favor of currying favor with a narrow and extreme political constituency."

Despite the victory celebrations and an impending North Dakota winter, protesters have vowed to stay camped on federal land until an alternate route is assured.

Last week New Mexico’s two Democratic senators asked Obama to intervene in the standoff, saying that protesters had been fired on with rubber bullets, tear-gassed and sprayed with water cannon during freezing temperatures.